#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
int main()
{
	int i, j;
	char letters[] = { "ABCDEFGHIJKLMEOPQRSTU" };
	for (i = 0; i <6; i++) {
		for (j = 0; j <=i; j++) {
			printf("%c", letters[j+i *(i+1)/2]);
		}
		printf("\n");
	}
	return 0;
}